Field of the Invention
The present invention relates to a display apparatus and a display method.
Description of the Related Art
Recently, in the field of image production, opportunities to handle image data (image data of a still image or a moving image) with a wider dynamic range than a conventional dynamic range have increased. Hereinafter, a conventional dynamic range will be described as a “standard dynamic range (SDR)” and a dynamic range wider than the SDR will be described as a “high dynamic range (HDR)”. Further, standards (for example, ST2084 standardized by the Society of Motion Picture and Television Engineers (SMPTE)) for transmitting HDR image data with a serial digital interface (SDI) cable are proposed. Techniques for displaying an HDR image with high brightness are also proposed. HDR image data refers to image data with an HDR, and an HDR image refers to an image based on HDR image data.
Meanwhile, in the field of broadcasting, broadcasts of SDR image data have become mainstream. SDR image data refers to image data with an SDR. Not all display apparatuses accommodate an HDR, and there are display apparatuses which do not accommodate an HDR. Therefore, there are cases where both HDR image data and SDR image data are generated. Methods of generating HDR image data and SDR image data include generating HDR image data by photography and then generating SDR image data by a grading operation based on the HDR image data. In a grading operation, there is a need to check an HDR image and an SDR image at the same time. Therefore, in a grading operation, both an HDR image and an SDR image may be displayed on a display apparatus. An SDR image refers to an image based on SDR image data.
Since HDR image data has a wide dynamic range, an HDR image is favorably displayed with high display brightness such as 1000 [cd/m2]. Display brightness refers to brightness of a screen. In addition, an SDR image is favorably displayed with display brightness (for example, 100 [cd/m2]) which is lower than the display brightness of an HDR image. Display brightness control methods include a method of controlling emission brightness of a backlight unit. Specifically, the method involves increasing display brightness by increasing the emission brightness of the backlight unit and reducing display brightness by reducing the emission brightness of the backlight unit. The emission brightness of a backlight unit refers to brightness of light emitted from the backlight unit.
By enabling the emission brightness of the backlight unit to be individually controlled in an area corresponding to a display area of an HDR image and an area corresponding to a display area of an SDR image, display of an HDR image with high brightness and an SDR image with low brightness can be realized by one display apparatus. A display area of an image is an area of a screen in which the image is displayed. However, adopting a configuration which enables emission brightness of a backlight unit to be partially changed significantly increases cost.
Techniques related to the control of display brightness include a technique disclosed in Japanese Patent Application Laid-open No. H5-300453. In the technique disclosed in Japanese Patent Application Laid-open No. H5-300453, for each of a plurality of blocks constituting a screen, image data corresponding to the block is corrected by correction data corresponding to the block. However, the technique disclosed in Japanese Patent Application Laid-open No. H5-300453 is a technique for reducing unevenness in brightness of a display image (an image displayed on the screen). Therefore, even when the technique disclosed in Japanese Patent Application Laid-open No. H5-300453 is used, an HDR image and an SDR image cannot be respectively displayed with favorable brightness (appropriate brightness).